Compass & Magnetic Declination
A baseplate compass is the simplest, most reliable navigation tool you can carry into gold country. It never needs batteries or signal, and paired with a topographic map it lets you fix your position, hold a direction across broken ground, and walk back out the way you came. But a compass needle points to magnetic north, not the north on your map. Closing that gap is the single most important skill in compass work, and it changes depending on where you stand.
Parts of a baseplate compass
A baseplate (orienteering) compass has a clear rectangular base you set on the map, marked with a direction-of-travel arrow and ruler scales. On top sits a rotating bezel, the housing, with the full 360 degrees printed around its rim. As USGS notes, the four cardinal points fall at north 0 (or 360), east 90, south 180, and west 270. Inside the liquid-filled housing the magnetic needle floats freely; its red end seeks magnetic north. Printed on the floor of the housing is an orienting arrow and a set of parallel orienting lines, which you line up with the map's north-south grid. Better models add an adjustable declination scale so you can build the local correction into the compass itself.
True, magnetic, and grid north
Three "norths" matter. True north (also called geographic or geodetic north) is the direction toward the geographic North Pole, the top of every map. Magnetic north is the direction your compass needle actually points, toward the wandering north magnetic pole. Grid north is the direction the vertical grid lines run on a projected map; because a curved Earth is flattened onto a flat sheet, grid lines and true north diverge slightly. USGS topographic maps print all three as a small diagram of arrows in the margin, with the angles between them shown.
What magnetic declination is
Magnetic declination, sometimes called magnetic variation, is the angle between magnetic north and true north at your location. NOAA's National Centers for Environmental Information (NCEI) defines declination as positive (east) when magnetic north lies east of true north, and negative (west) when it lies to the west. Two facts make declination unavoidable. First, it varies by place: across the United States the correction can swing well over twenty degrees from one region to another, so a value good in one state is wrong in the next. Second, it drifts over time, because the magnetic pole slowly moves. NOAA models this with the World Magnetic Model and IGRF, and USGS warns that the declination printed on an old map may no longer be accurate. A correction that is even a few degrees off, ignored over a mile, can put you hundreds of feet from where you intend to be.
Adjusting for declination
To convert between a map (true) bearing and a field (magnetic) bearing you apply the local declination. The common rule of thumb is "east is least, west is best": for an east declination you subtract it from the true bearing to get the magnetic bearing, and for a west declination you add it. The cleaner solution USGS recommends is an adjustable-declination compass: set the local angle once on the compass, and from then on the magnetic needle and the bezel readings agree with your map automatically, removing the chance of adding when you should subtract. Either way, always look up the current declination for your specific area before a trip rather than trusting the map margin.
Taking and following a bearing
To take a bearing from the map, lay the compass edge along your line of travel from where you are to where you want to go, then rotate the bezel until its orienting lines parallel the map's north-south lines (the needle is ignored for this step). Read the bearing at the index. Adjust for declination if your compass is not already set. To follow that bearing on the ground, hold the compass level in front of you and turn your whole body until the red needle sits inside the orienting arrow (boxing the needle); the direction-of-travel arrow now points the way. Pick a distant landmark on that line, walk to it, and repeat, so small errors do not accumulate.
Triangulation (resection) to fix your position
If you can see two or three identifiable landmarks that also appear on your map, you can find where you stand. Sight each landmark, read its magnetic bearing, convert to a map bearing, then reverse it (add or subtract 180) and draw that back-bearing as a line through the landmark on the map. Repeat for a second and, ideally, a third landmark. The lines cross at your position. USGS guidance on map control notes that a point fixed by only two sights is of doubtful value, so a third sight is strongly preferred; with three, the small triangle they form brackets your true location.
In Lodester
Lodester is built to pair with a field compass, so the map and the needle work as one system. Before heading out, check the current magnetic declination for your prospecting area, because the value changes by location and drifts year to year under NOAA's model. Set that angle on your adjustable compass, or apply it by hand, so a bearing you read from a Lodester map can be walked directly in the field, and a bearing you shoot in the field plots correctly back on the map. Use that link to follow a line to a claim corner or sample site, and to resect off visible ridges and peaks when you want to confirm where you are. None of this is legal or safety advice; carry a backup means of navigation and know your skills before relying on a single tool.